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Serial Peripheral Interface (SPI)
MC68360 USER’S MANUAL
RAM values will not normally need to be accessed by user software. They should only be
modified when no SPI activity is in progress.
7.12.5.3.1 BD Table Pointer (RBASE, TBASE). The RBASE and TBASE entries define
the starting location in the dual-port RAM for the set of BDs for receive and transmit func-
tions of the SPI. This provides a great deal of flexibility in how BDs for an SPI are partitioned.
By setting the W-bit in the last BD in each BD list, the user may select how many BDs to
allocate for the transmit and receive side of the SPI. The user must initialize these entries
before enabling the SPI. Furthermore, the user should not configure BD tables of the SPI to
overlap any other serial channel’s BDs, or erratic operation will occur.
NOTE
RBASE and TBASE should contain a value that is divisible by 8.
7.12.5.3.2 SPI Function Code Registers (RFCR, TFCR). The FC entry contains the value
that the user would like to appear on the function code pins (FC3–FC0), when the associ-
ated SDMA channel accesses memory. It also controls the byte-ordering convention to be
used in the transfers.
Receive Function Code Register
Bits 7–5—Reserved
These bits should be set to zero by the user.
MOT—Motorola
This bit should be set by the user to achieve normal operation. MOT must be set if the
data buffer is located in external memory and has a 16-bit wide memory port size.
0 = DEC and Intel convention is used for byte ordering—swapped operation. It is also
called little-endian byte ordering. The bytes stored in each buffer word are reversed
as compared to the Motorola mode.
1 = Motorola byte ordering—normal operation. It is also called big-endian byte order-
ing. As data is received from the serial line and put into the buffer, the most signif-
icant byte of the buffer word contains data received earlier than the least significant
byte of the same buffer word.
FC3–FC0—Function Code 3–0
These bits contain the function code value used during this SDMA channel’s memory ac-
cesses. The user should write bit FC3 with a one to identify this SDMA channel access as
a DMA-type access. Example: FC3–FC0 = 1000. To keep interrupt acknowledge cycles
unique in the system, do not write the value 0111 binary to these bits.
Transmit Function Code Register
76543210
—
MOT
FC3–FC0
76543210
—
MOT
FC 3–FC0
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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